Abstract13.1 Spectral classification for bounded operators13.2 Spectra for operators on a Banach space13.3 Symmetric, self-adjoint, and unbounded operators13.4 Bounded operators and numerical range13.5 Self-adjoint operators13.6 Normal operators and nonbounded operators13.7 Spectral decomposition13.8 Spectra for self-adjoint, normal, and compact operators13.9 Pure states and density functions13.10 Spectrum and resolvent set13.11 Spectrum for nonbounded operators13.12 Brief descriptions of spectral measures and spectral theoremsReferences